Fire tube boiler with spiral ribbon burner



United States Patent [72] inventor Frank Gething Milwaukee, Wisconsin [21 Appl. No. 753,420 [22] Filed Aug. l9, i968 Division orser."No.ss1,s40,ol9, 1966,

No. 3,438,179, Apr. 15, 1969 [45] Patented Sept.22 l9 7ll M H [73] Assignee Aqua-Chem, Inc.

Waukesha,Wisconsin a corporation of Wisconsin [54] FIRE TUBE BOILER WITH SPIRAL RIBBON BURNER 5 Claims, 6 Drawing Figs.

[52] U.S. Cl. 122/45 F22b 9/04 [50] Field of Search 122/45,

[56] References Cited UNITED STATES PATENTS 2,368,467 l/l945 l-lainsworth 122/137 2,431,753 12/1947 Holderle et al. 122/1 36X 2,855,903 10/1958 Bliss 122/149 Primary Examiner-Kenneth W. Sprague Attorney- Hofgren, Wegner, Allen, Stellman and McCord ABSTRACT: A tire tube boiler having a heat exchange chamber defined on each end by tube sheets with a plurality of fire tubes extending between said sheets. The boiler has a burner assembly mounted outwardly of one of the tube sheets with burner elements uniformly spaced from the tube sheet and having a burner element in alignment with each fire'tube. The burner assembly has a plurality of headers for feeding a combustible mixture to the burner elements. A means is provided for igniting adjacent burner elements from a lighted element and deflector means are provided for preventing flame from said means from directly engaging said tube sheet.

FIRE TUBE BOILER WlTl-l SPIRAL RIBBON BURNER This application is a divisional application of the application of Frank Gething, Ser. No. 587,840, filed Oct. l9, 1966, entitled Spiral Ribbon Burner", now US. Pat. No. 3,438,7 l 9.

This invention relates in general to an improved burner construction, and more particularly to a burner construction for use in a fire tube boiler.

ln the past, it has been well known to provide a boiler construction wherein a plurality of fire tubes extend longitudinally through a heat exchange chamber containing water or the like. It has also been known to provide individual burners for each of the fire tubes adjacent one end thereof for igniting a gas-air mixture. While such boiler constructions have in general functioned satisfactorily, heretofore, it has not been possible to modulate the firing rate of the boiler; and consequently these boilers have strictly been on-off units. Modulation of fire tube boilers has heretofore not been possible, because of a flashback phenomenon, that is, a lighting of the combustible mixture in the burner manifolds and burner pipes, when the burner is turned down from a maximum rating to an intermediate or low rating. The flashback phenomenon occurs because burners that have been used in the past eject the combustible mixture through a relatively large hole, for example, 1%" to 1 diameter; and with such a hole size, the velocity of mixture therethrough at intermediate or low firing rates is sufficiently slow that flashback occurs in the mixture feeding manifolds. Accordingly, the general purpose of the present invention is to provide an improved burner construction for a fire tube boiler which will eliminate the flashback phenomenon during intermediate and low firing rates, so that the firing rate of the boiler can be generally universally modulated.

An object of the invention is to provide an improved burner construction for a fire tube boiler which will provide uniformity of firing throughout the boiler, so that there will be uniform heat transfer to the substance being heated.

Another object of the invention is to provide a burner for a fire tube boiler having a configuration such that localized flames of high capacity are provided, which can be spaced as desired.

A further object of the invention is to provide an improved burner header construction which enables individual burners to light adjacent burners without the flame impinging upon the tube-sheet ligaments between the burners.

Still another object of the invention is to provide a burner construction as described in the preceding paragraph with flame deflector means arranged to space the burners a desired distance from the tube sheet, thereby giving uniform spacing between each of the burners and the ends of the fire tubes.

A still further object of the invention is to arrange the flame deflector means of a burner as described above, so that it will be cooled by the water withing the boiler via the engagement of the flame deflector means with the tube sheet.

Still another object of the invention is to provide a plurality of rows of burner headers arranged such that a single pilot burner at one end of the rows can ignite each of the burners.

These and other objects of the invention will hereinafter become more fully apparent from the following description taken in connection with the annexed drawing, wherein:

FIG. 1 is a perspective view of a boiler having the burner means of the present invention incorporated therein, with certain portions of the boiler being broken away for clarity of illustration;

FIG. 2 is a broken front view of a burner header; 7

FIG. 3 is an enlarged cross sectional view taken generally along line 3-3 of FIG. 2;

FIG. 4 is an enlarged cross sectional view taken generally along the line 4-4 of F IG. 2;

FIG. 5 is an enlarged perspective view of a ribbon burner element; and

FIG. 6 is a perspective view of the means for securing one end of the ribbon burner element.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail a preferred embodiment of the inven tion with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring now to the drawing, wherein like reference characters designate like or corresponding parts throughout the several views, a fire tube boiler is designated in its entirety by reference numeral 10 in FIG. 1, and includes a generally cylindrical shell 11 defining a heat exchange chamber 12 therewithin. A plurality of horizontally aligned rows of tubes 13, which are preferably dimpled, extend longitudinally from end to end of chamber 12, and the ends of tubes 13 are held within tube sheets 14 and 15 at opposite ends of the shell 11. A burner assembly 16 is provided at one end of boiler 10 outwardly of tube sheet 15, and burner assembly 16 is preferably housed within a cover box 17 that may be hingedly connected to the shell 11 and sealed thereto by a gasket when closed, so that the burner assembly is completely enclosed. Burner as sembly 16 includes a plurality of horizontally extending burner headers 18, each of which is provided with a plurality of horizontally spaced burners for providing a flame within each of the tubes 13. The spent combustion gases pass from right to left, as viewed in FIG. 1, through the tubes 13 in a single pass through the heat exchange chamber 12, and the exhaust gas passes outwardly of the boiler 10 from a stack 19 communicating with an exhaust chamber defined between tube sheet 14 and an inclined baffle plate 20.

Air for combustion is drawn inwardly of the boiler shell 11 by a fan 21 that is driven by a motor M, and the air is forced through primary conduits 22 and 23 and mixed with gas from supply line 25 in venturi assemblies 26 at opposite sides of the boiler. The gas-air mixture is conveyed through supply manifolds 27 and 28 at opposite sides of the boiler into the headers 18, and secondary air is forced through a conduit 24 by fan 21 into the plenum chamber defined behind the burner assembly 16 and the cover 17. Supports S extend upwardly from pipes 22, 23 and 27 to the boiler shell 11; so that the pipes serve as supports for the boiler shell, as well as to convey the gas-air mixture to the burner asembly. Linkage operated damper means D is provided in the air lines, and as the amount of air is increased, the amount of gas drawn in increases proportionately to give a proper combustible mixture in the burner assembly 16. While gas-air supplies are illustrated in FIG. 1 at opposite sides of the burner assembly 16, it will be apparent from the following description that the mixture may be provided at only one side of the assembly, if desired.

The headerconstruction 18 illustrated in detail in F IGS. 2 4 is usable in a structure wherein only a single supply manifold 28 is provided, in that the header 18 is provided with an elbow connector 32 at one end for connection with the manifold 28, and a plate 31 that closes the opposite end of the header. However, in the arrangement such as that illustrated in FIG. 1, wherein manifolds 28 are provided at opposite ends of the burner assembly 16, the headers 18 would be provided with elbow connectors 32 at opposite ends thereof connected with respective manifolds 28. As can be seen in FIGS. 3 and 4, headers 18 are generally cylindrical tubes, and spaced circular openings 33 are provided in one side thereof, with an upright wall 34 extending substantially peripherally around each opening 33. Elongate slots 35 connect adjacent openings 33, and upstanding walls 36 are provided at opposite sides of each slot 35. Headers 18 are preferably formed by machining an elongate continuous slot in the side wall of the header, and then drawing inserts upwardly from within the header to form the circular openings and the upstanding walls therearound.

' Burner discs 37 are provided in each opening 33, and each burner disc 37 is formed of a single length of ribbon type of burner element, such as that shown at 38 in FIG. 5. The ribbon element 38 is preferably formed of stainless steel, although galvanized steel or even brass would be suitable, and the ribbon element is defined by a plurality of lengths of material 39 connected by corrugations 40. Each disc 37 includes a pin 41 at the center thereof, and pins 41 have a flat surface 42 at one side thereof to which the end of ribbon element 38 is attached, as by spot welding. The ribbon element 38 is then tightly wound about pin 41 in spiral fashion, and the corrugations 40 cooperate with the lengths of material 39 on adjacent convolutions to define relatively small outlet openings 43 therebetween. The thus formed burner discs are inserted within each opening 33 in header 18, and a hole is formed diametrically through each disc 37, including ribbon element 38, center pin 41 and side wall 34. A pin 44 is then inserted through each hole to position and retain the discs 37 on the headers 18, and the outer ends of pin 44 are welded at 45 to the side wall 34.

Straight ribbon inserts 46 are provided in each of the slots 35, and inserts 46 are made by sandwiching straight lengths of ribbon elements 38 between flat side walls 47, forming a hole through inserts 46 and the side walls 36, and inserting a pin 48 through above described hole. The outer ends of pin 48 may be spot welded at 49 to the wall 36. Flame deflectors 50, of inverted U-shaped configuration, are then placed over the inserts 46 with the legs 51 and 2 of flame deflectors 50 being welded to the walls 36 at 53. Flame deflectors 50 are substantially the same length as inserts 46, and the bight portion of the flame deflectors provides a flat outer surface 54.

When the discs 37, inserts 46, and flame deflectors 50 have been assembled to each header 18, the headers are then assembled to the manifolds 28 to form the burner assembly 16. The burner assembly 16 is then positioned adjacent the tube sheet 15. and as is evident from FIG. 4, the outer surfaces 54 of flame deflectors 50 abut against the outer surface of the tube sheet 15. This enables the burner discs 37 to be spaced an appropriate amount from the ends of tubes 13, as is evident from FIG. 3, it being understood that each burner disc 37 is positioned in longitudinal alignment with one tube 13. a single, vertically aligned pilot sandwich burner (not shown) may be positioned forwardly of the outermost disc 37 in each header 18 to impinge upon the gas-air mixture issuing therefrom to ignite the same. The flame issuing from each burner disc 37 will be dircted longitudinally into its associated tube 13, and the gas-air mixture supporting the flame will pass outwardly of the disc 37 through the small openings 43 at high velocity, so as to obviate the possibility of flashback in header 18 or manifold 28. The gas-air mixture will also pass through the small openings formed between the sandwiched layers of the inserts 46, and the gas issuing therefrom will be lighted from an adjacent burner disc 37, so that each of the burner discs in a particular header is ignited from an adjacent insert 46. Flame deflectors 50 are formed of a suitable heat resistant material, such as stainless steel and effectively prevent the flame issuing from the inserts 46 from impinging upon the tube sheet 15, while still allowing ignition from one disc 37 to an adjacent disc 37. Because of the relatively large, facial engagement between flame deflector 50 and tube sheet 15, the

water or other substance within heat exchange chamber 12 will have a substantial cooling effect on the flame deflectors.

In an exemplary embodiment of the invention, wherein the fire from disc 37 passes into a 2%" boiler tube, the capacity of each of the burner discs 37 is 125,000 Btu. per hour with a mixture pressure of 4" W.C. In a boiler having boiler tubes 13, the total input rate to the boiler is 12,500,000 Btu. per hour, and the uniformity of firing with such a boiler can be readily visualized. Thus, it is submitted that the unique burner construction of the present invention fully achieves each of the objects of the invention.

lclaim:

1., A fire tube boiler comprising: a shell defining a heat exchange chamber therewithin; first and second tube sheets adjacent opposite ends of said shell; a plurality of fire tubes extending through said heat exchange chamber and having the outer ends thereof mounted in said tube sheets; and a burner assembly at one end of said shell outwardly of said first tube sheet, said burner assembly including a burner element for each fire tube, said burner assembly including a plurality of headers, each having a combustible mixture flowing therethrough and each having a plurality of burner elements spaced therealong, means for spacing each of said burner elements a uniform distance from its respective fire tube, said means for spacing being provided on each header between adjacent burner elements, and means associated with each header between each of said burner elements for igniting from burner element to burner element, said means for spacing being arranged to arrest the flame between the burner elements to prevent the flame from impinging upon the first tube sheet.

2. A fire tube boiler as set forth in claim 1 wherein said means for spacing is defined by flame deflector elements which are generally U-shaped in cross section, the legs of said flame deflector elements being secured to said headers between said burner elements, and the bight portions of said flame defelector elements including a flat outer surface positioned in face abutting engagement with said first tube sheet.

3. A fire tube boiler comprising: a shell; a heat exchange chamber within said shell defined by a pair of spaced apart tube sheets; a plurality of fire tubes having their ends mounted in said tube sheets and passing through said heat exchange chamber; a burner assembly carried by the shell and spaced from one of said tube sheets; a burner element on said burner assembly for each fire tube; a burner disc in each burner element defined by a single spirally wound length of ribbon burner element; and means between each burner element for igniting adjacent burner elements from a lighted burner element.

4. A fire tube boiler as set forth in claim 3 wherein a flame deflector means is mounted between adjacent burner elements to prevent the flame from impinging directly on said tube sheet.

5. A fire tube boiler as set forth in claim 4 wherein said flame arrestor means is in contact with said tube sheet whereby heat is exchanged from said flame arrestor to the fluid in said heat exchange chamber through said tube sheet. 

